Background
Belt et al. (2007) recently proposed the use of a novel biomarker (IP25), which the authors describe as a mono-unsaturated highly-branched isoprenoid that is synthesized by sea ice diatoms that have been shown to be stable in sediments below Arctic sea ice.

What was done
Based on IP25 data obtained from a marine sediment core retrieved from Barrow Strait (74°16.05'N, 91°06.38'W), which they compared with "complementary proxy data obtained form analysis of other organic biomarkers, stable isotope composition of bulk organic matter, benthic foraminifera, particle size distributions and ratios of inorganic elements," the five UK scientists developed a spring sea ice record for that part of the central Canadian Arctic Archipelago.

What was learned
Vare et al. discovered evidence for a decrease in spring sea ice between approximately 1200 and 800 years before present (BP), which was followed by an increase in sea ice over the last 400 years of their record (between 800 and 400 years BP). "Interestingly," as they describe it, "these latter two intervals coincide with, respectively, the so-called Mediaeval Warm Period and Little Ice Age, which commonly feature in lower latitude palaeo-climatic studies."

What it means
The researchers say they anticipate that the data set from their study "will be important for further palaeo-climate reconstruction and for future climate prediction models," and in this they are correct. We will soon be adding its findings to our Medieval Warm Period Project, for example, where it will further demonstrate the global nature of the MWP, which other data suggest was often warmer that what the earth has been during the Current Warm Period, which observation does not accord well with state-of-the-art climate model simulations.